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From Divyaprakash Y <>
Subject RE: Packet misses in Tomcat
Date Mon, 06 Jan 2014 18:13:09 GMT
>> Issue: Few packets do not reach the application servlet but tomcat receives them.
The missing packets reach the HTTP layer and thereafter they disappear.
>> This issue is not frequent but occasionally consistent. For the POSTs of missing
packet I am not able to find the entry in localhost_access_log.
>> How do you know that the packet reaches tomcat if there is no matching entry in localhost_access.log?
Does all other access appear in this file?
> I could see the packet in the wireshark capture and it has reached HTTP layer so I thought
it has reached Tomcat; I may be wrong here. Also, as far as my observation, every hit to the
application URLs was getting logged in local access log.

And is there anything in the Tomcat error logs ?
(Or the Windows Event logs)

A HTTP request might be discarded by Tomcat for various reasons (*) before it is ever
mapped to an application.
In such a case, there is probably also no log of the request in the Access log.
But I would expect some error message in the Tomcat error logs.

(*) Invalid HTTP request, incomplete request, etc..
If there are really packets being lost somewhere, then for POST requests the request size
would not match the Content-length header, and that may be one of these cases.

I must say that the "packets lost" hypothesis sound a bit iffy to me.
This is TCP, which should detect missing packets and cause a client connection abort if it
was the case.  The invalid HTTP request being rejected by Tomcat sounds more probable to me.
I could not find anything (Exception) in tomcat std error log file or any file in the log
folder. But I  have not checked the Windows event logs. Will do that.

Regarding the content length, there is no mismatch as I have validated using Wireshark and
also the same packets(In terms of structure) have reached the application previously.

W.r.t. the last point, I could see TCP ACK for the received packet in the wireshark and the
packet has reached HTTP layer which goes missing thereafter.

Is there any configuration to get more logs on the operations happening during the mapping
of request to the application?

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